Not only are species which are known to be poisonous to be avoided, but discretion should be used in eating recognized good species. Fungi undergo chemical changes so rapidly that even the cultivated mushroom may cause inconvenience if kept so long after being gathered as to undergo chemical change. It is not enough that they should be of a good kind, but also fresh. The employment of plenty of salt in their preparation is calculated very much to neutralize any deleterious property. Salt, pepper, and vinegar are much more freely employed abroad in preparing fungi than with us, and with manifest advantage. It is undoubtedly true that fungi exert an important influence in skin diseases. This seems to be admitted on all hands by medical men,[E] however much they may differ on the question of the extent to which they are the cause or consequence of disease. Facts generally seem to bear out the opinion that a great number of skin diseases are aggravated, and even produced, by fungi. Robin[F] insists that a peculiar soil is necessary, and Dr. Fox says it is usually taught that tuberculous, scrofulous, and dirty people furnish the best nidus. It is scarcely necessary to enumerate all these diseases, with which medical men are familiar, but simply to indicate a few. There is favus or scall-head, called also "porrigo," which has its primary seat in the hair follicles. Plica polonica, which is endemic in Russia, is almost cosmopolitan. Then there is Tinea tonsurans, Alopecia, Sycosis, &c., and in India a more deeply-seated disease, the Madura Foot, has been traced to the ravages of a fungus described under the name of _Chionyphe Carteri_.[G] It is probable that the application of different names to the very often imperfect forms of fungi which are associated with different diseases is not scientifically tenable. Perhaps one or two common moulds, such as _Aspergillus_ or _Penicillium_, lie at the base of the majority, but this is of little importance here, and does not affect the general principle that some skin diseases are due to fungi.